Cochlear implant systems are used to provide the sensation of hearing to those who are profoundly deaf, and for whom traditional hearing aids are of little or no assistance due to disease or damage to the middle ear or inner ear. A cochlear implant system provides the sensation of hearing by applying electrical stimuli to the inside of the scala tympani duct of the cochlea, thereby directly stimulating the ganglion cells coupled to the auditory nerve. Once stimulated, such ganglion cells send nerve impulses to the brain through the auditory nerve which are sensed in the brain as perceived sound.
A cochlear implant system typically includes implanted and external components. The implanted components include a pulse generator and an electrode, inserted into the cochlea, through which the electrical stimuli are applied. The external components include a power source, a microphone, a speech processor, and a headpiece. The microphone senses sound waves in conventional manner and converts such sensed sound waves to an electrical signal. This electrical signal is then processed by the speech processor and converted into an appropriate control signal for sending to the implanted pulse generator (also referred to as an "implanted stimulator"). A representative cochlear implant system is described in U.S. Pat. No. 5,776,172, incorporated herein by reference.
In operation, the control signal is sent to the implanted pulse generator through a transmission coil located in the headpiece, and is received through a corresponding coil included within the implanted pulse generator. In order to operate efficiently, i.e., in order for the headpiece to be able to transcutaneously send the control signal (i.e., transmit the control signal through the skin) to the implanted pulse generator, it is necessary that the external transmission coil of the headpiece be placed as close as possible to, and be properly aligned with, the receiving coil within the implanted pulse generator.
The most common technique for retaining the transmitting coil in a transcutanious-type cochlear implant system is the use of two magnets. One magnet is placed inside the implanted stimulator in the center of the receiving coil. The other magnet forms part of the transmitting coil.
The use of two magnets as described is very simple, effective and cosmetically attractive. However, there are a growing number of patients who are either unable or do not want to use this technique due to, inter alia, the concern that the internal magnet may interfere with MRI (magnetic resonance imaging) diagnosis.
To address such concerns, cochlear implant manufacturers have considered providing a number of options for holding the headpiece of the cochlear implant system in alignment with the implanted portion. Examples of such options include:
1. a non-magnetic implant; PA1 2. an ear mold retention mechanism; PA1 3. attachment of the headpiece to the arms of spectacles or eye glasses; PA1 4. gluing the headpiece to the shaved skin with adhesive tape; PA1 5. holding the headpiece in place with a headband; or PA1 6. using other alignment/holding components and devices, glued to the skin, such as shown in U.S. Pat. No. 5,545,191, also incorporated herein by reference.
Disadvantageously, all of the above-listed alternatives have significant limitations. First, they are generally strongly dependant on the customization of the products to suit the individual anatomical requirements of the patients. In the case of ear mold retention, it is not cosmetically attractive, and for some patients, not a comfortable solution.
There is thus a need for a more universal, cosmetically acceptable, and more comfortable solution for holding the headpiece of a cochlear implant system in alignment with the receiving coil of an implanted stimulator.